装甲型 BCMA CAR-T 细胞清除多发性骨髓瘤并抵抗 TGF-β 的抑制作用

CAR T-cell therapies targeting the B-cell maturation antigen eliminate tumors in relapsed/refractory multiple myeloma patients, however durable remissions remain difficult to attain. Transforming growth factor beta (TGF- ) is a multifunctional cytokine abundantly expressed in the multiple myeloma bone marrow niche, where it promotes an immunosuppressive tumor microenvironment.

We hypothesized that BCMA CAR T-cells armored to resist the suppressive effects of TGF- will provide an advantage in treating multiple myeloma. The armored B2ARM CAR T cells, co-expressing BCMA targeting CAR with TGF- dominant-negative receptor II, were generated by lentiviral transduction of primary human CD4+ and CD8+ T cells. The B2ARM CAR T cells eliminated MM.

1S multiple myeloma targets in long-term cytotoxicity assays, even under TGF- -high conditions, whereas cytotoxic function of the non-armored B2 CAR -T cells was inhibited by TGF- . Concordantly, after long-term exposure to targets in the presence of TGF- , the B2ARM CAR T cells were enriched for Granzyme B, CD107a, Ki67 and polyfunctional cells T-cells (double or triple-positive for IFN- , IL-2 and/or TNF- ), as determined by flow cytometry.

In addition, the B2ARM CAR T-cells, but not the conventional B2 CAR T-cells, resisted the TGF- -mediated suppression of activation (CD25), exhaustion (PD-1, LAG3), and differentiation to T effectors (CD45RA+ CD45RO-CD62L-). In NSG mice bearing RPMI-8226 tumors overexpressing TGF- , the B2ARM CAR mediated 100% tumor rejection and survival, superior infiltration of tumors on day 7 post CAR T treatment (%CD3+CAR+), and greater expression of IFN- , TNF- , Ki67, Granzyme B, and PD-1, as compared to tumor-infiltrating non-armored B2 CAR T-cells.

In NSG RPMI-8226 xenograft model in which tumors were additionally supplemented with TGF- injections on days -1 through 11 of CAR T treatment, the B2ARM CAR T cells rejected tumors faster than the non-armored B2 CARs, and showed greater numbers of CD3+ and CD3+CAR+, central memory (CD45RO+CD62L+) and effector memory (CD45RO+CD62L-) T cells in the peripheral blood 18 days after treatment.

In summary, the armored B2ARM CAR T cells mediate superior persistence, proliferation, multi-functionality, effector differentiation and anti-tumor function in pre-clinical models of multiple myeloma, while abrogating TGF- -mediated suppression.